This invention relates to a rubber composition for tire tread, and a pneumatic tire using the rubber composition.
Wet silica has been traditionally known as a filler which can achieve a balance between reduced heat generation and the grip properties on wet road surfaces, which are needed by pneumatic tires as required performances. This wet silica has a tendency that particles aggregate as a result of hydrogen bonding between silanol groups, which are the surface functional groups of the wet silica. Thus, since dispersion of wet silica in rubber is deteriorated, a decrease in wear resistance is not avoided, and in order to improve dispersion of silica in rubber, it is necessary to lengthen the kneading time.
In order to ameliorate these defects, silane coupling agents have been developed.
The Yokohama Rubber Co., Ltd. has hitherto proposed a rubber composition for tires, which contains a condensate of 3-octanoylthio-1-propyltriethoxysilane (JP 2006-232917 A).
Furthermore, a rubber composition containing specific silica and a SH-based silane coupling agent having a specific structure in a diene-based rubber has been proposed (for example, JP 2009-263420 A).